1. Field of the Invention
The present invention relates to a battery protective circuit of portable cassette recorder (or radio), and more particularly to a battery protective circuit, being utilized in the portable cassette recorder equipping both battery and re-charger, which can prevent unnecessary consumption of battery power generated by re-charger being charged by the battery power when the voltage of battery is higher than that of a re-charger.
2. Description of the Prior Art
Generally, the portable cassette recorder utilizing re-charger is provided with a separate battery pack in which conventional batteries are inserted, and a re-charger is mounted to the inside of cassette recorder for use.
Furthermore, when there is a separate power source, said power source can be utilized by using an adapter, and when adapter is used, the battery and re-charger are designed to be separated by circuit, so that re-charger can be charged.
Meanwhile there are several kinds of re-chargers such as sulfer/natrium battery, Nicad battery and the like, and every re-charger has a larger capacity than the battery and can obtain the desired level of voltage and current only when re-charged more than predetermined period of time.
Specifically, when the power of conventional battery somehow flows into said re-charger by unknown reason, only quite small amount of power is charged with said re-charger if compared with the amount of power consumed in the battery.
In the meantime, as conventional portable cassette recorder has a construction having a re-charger and a battery wired on the same power line, and when the voltage of a re-charger is lower than that of a battery, current flows from the battery to the re-charger.
At this point, the battery consumes power unnecessarily due to said characteristics of a re-charger.
In this manner, due to unnecessary power consumption of a battery in the conventional power circuit, one disadvantage is that the life span of a battery becomes shortened, and more specifically, in the case of portable cassette recorder using small capacity of batteries, there has been a disadvantage of shortened time in the use of batteries.